In a case where a thermoplastic resin composition is used for various applications such as housings of a personal computer and a display device, an electronic device material, automotive exterior and interior parts, and the like, there sometimes occurs a problem that it is difficult to release generated heat because plastic is less thermally conductive than an inorganic substance such as a metal material. In order to solve such a problem, an attempt has been extensively made to obtain a highly thermally conductive resin composition by blending, with a thermoplastic resin, a highly thermally conductive inorganic compound in a large amount. In order to obtain a highly thermally conductive resin composition, it is necessary to blend, with a resin, a highly thermally conductive inorganic compound such as graphite, carbon fiber, alumina, or boron nitride generally in an amount of not less than 30 vol % and further in an amount of as many as not less than 50 vol %. However, when an inorganic compound such as graphite or carbon fiber is blended in a resin in a large amount, the resin will have a reduced electrical insulation property and thereby become electrically conductive. This causes a problem that only a limited portion of the resin can be used in an electronic device application. Further, when a ceramic filler such as alumina is blended in a resin in a large amount, the resin will cause abrasion on a mold due to a high hardness of the filler, in a case where the resin is used as a molding material. Further, since a high density of the filler will increase the density of an obtained composition, the resin makes it difficult to reduce the weight of an electronic device or the like. Another approach to use a filler which has a relatively low density and hardness, such as a boron nitride filler, has also been reported. However, even if such filler is used, it is inevitable that blending an inorganic compound with a thermoplastic resin significantly lowers molding processability of a resin composition, as long as the inorganic compound is added to the resin in a large amount. This is because an inorganic compound cannot be dissolved at a molding temperature of a resin.
From such a viewpoint, it has been strongly desired to develop a thermally-conductive organic additive which (i) has properties such as a low density, a low hardness, and an electrical insulation, and (ii) can be dissolved at a molding temperature of a resin.
Epoxy resins described in Patent Literatures 1 and 2, or bismaleimide resins described in Patent Literature 3, for example, have been reported as a thermosetting resin in which a resin per se has an excellent thermal conductivity. Unfortunately, these resins cannot improve molding processability of a resin composition since the resins have a thermosetting property and are not dissolved at the molding temperatures of the resins.
In contrast, there have been some examples of researches on a thermoplastic resin as to a special molding process such as extension or magnetic field orientation during an injection molding process so as to give the thermoplastic resin a high thermal conductivity in a specified direction. However, these techniques are not applicable to a thermally-conductive organic additive.